Interface and abstract class

Question

hi friends what is the difference between interface and abstract class? please justify in which case we use interface and in which case we use abstract class .

Datta Kharad · Answer

Hi Abstract Class:- An abstract method is created by specifying the abstract type modifier. An abstract method contains no body. An abstract method is not implemented by the base class. An abstract method is automatically virtual. A derived class must override it. Abstract class can have modifiers for methodsproperties etc. An abstract class can implement a property. The abstract modifier cannot be applied to static methods. Properties can also be abstract. A class containing abstract methods must be declared as abstract with the abstract specifier. There can be no objects of an abstract class. If a derived class doesn't implement all of the abstract methods in the base class then the derived class must also be specified as abstract. An abstract class can inherit from a class and one or more interfaces. An abstract class can implement code with non-Abstract methods. Abstract class can have constant and fields. An abstract class can have constructors or destructor's. An abstract class cannot be inherited from by structures. An abstract class cannot support multiple inheritance. If we add a new method to an abstract class then we have the option of providing default implementation and therefore all the existing code might work properly. Interface :- Interfaces cannot be instantiated directly. Interfaces can contain events method indexer and properties. An Interface can contain property definitions. Interfaces contain no implementation of methods. Classes and Structs can implement more than one interface. An Interface can be inherited from by structures. An interface itself can inherit from multiple interfaces (Interface can support multiple inheritance) . An abstract class can implement a property. If we add a new method to an Interface then we have to track down all the implementations of the interface and define implementation for the new method.

Milan Zipancic · Answer

Use interface: - Do you want to inherit multiple classes? It is not possible in C# but one class can implement more interfaces at the same time. - Class does something interface represents something. Interfaces could be independent from what class does. - If many classes inherit form one base (abstract) class you will be fillled with too many tiny functionalities. Use abstract class: - Is there a reasonable amount of common functionalities and data to use in all subclasses? If there is use absract base class. If you use same interface in multiple classes you might have case of a code repeatation. - Abstract class allows you to define some methods with not just theirs signature (access modifier return type method name parameters) but also with body. So full declaration is possible. Actually you can provide full declaration for all methods but one. You will have to define at least one method declaration with no body defined for it just siganture (as for interfaces). In this way comparing to interface abstract class can force a specific method implementation and this can be useful sometimes. With interface you have no control over method implementation.

Satyapriya Nayak · Answer

Hi Akshay Please refer Our recommended articles. Thanks

Vulpes · Answer

Check out my answer to a similar question on this thread: http://www.c-sharpcorner.com/Forums/Thread/110425/what-is-abstract-class-and-interface-and-where-exactly-s.aspx